You can't the way the code is written. It is based on the outline level and Word has a hard limit of 9 outline levels for any outline list. The code gets to a 10th level by using 'no outline list' as the tenth level.

You would need a completely different approach to go beyond the constraints of using the outline lists. Create your own custom styles and forget the outline levels. For instance: Gen01, Gen02, ... , Gen09, Gen10, Gen11, Gen12 etc.
Once the styles are created, the code could be altered to correspond with that method of applying a hierarchy.

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Andrew Lockton
Chrysalis Design, Melbourne Australia